A liquid crystal display device has such advantages as a light and thin body and low power consumption. Because of the advantages, a liquid crystal display device is utilized for not only a small-size display device such as a display portion of a mobile telephone, but also a large-size television set. As for a liquid crystal panel, the liquid crystal panel itself does not emit light, unlike a self-emitting panel such as a cathode ray tube (CRT) and a plasma display panel (PDP). Accordingly, a liquid crystal display device generally performs display by utilizing light of a backlight disposed on a back side of a liquid crystal panel.
In recent years, unlike a general liquid crystal display device with three primary colors, a liquid crystal display device with four or more primary colors which are additively mixed is suggested. Such a liquid crystal display device is also referred to as a multi-primary color liquid crystal display device. In general, in a multi-primary color liquid crystal display device, any other primary color is added to the three primary colors (i.e., red, green, and blue), thereby increasing the color reproduction range. The multi-primary color liquid crystal display device performs display in such a manner that grayscale levels of an input video signal which can be displayed by a general three-primary color display device are converted into grayscale levels of four or more primary colors (see Patent Documents No. 1 and No. 2, for example). Such conversion is also referred to as multi-primary color conversion.